<embed type="application/x-test" width="200" height="200"></embed>

<script>

var plugin = document.querySelector("embed");

function startAudio() {

  plugin.startAudioPlayback();

}

function stopAudio() {

  plugin.stopAudioPlayback();

}

function pluginMuted() {

  return plugin.audioMuted();

}

function toggleMuteState(muted) {

  var Ci = SpecialPowers.Ci;

  var utils = SpecialPowers.wrap(window).top

                           .QueryInterface(Ci.nsIInterfaceRequestor)

                           .getInterface(Ci.nsIDOMWindowUtils);

  utils.audioMuted = muted;

}

</script>